The present invention relates to a method for controllably altering the conductivity of a body of glassy amorphous material and electronic devices which can be produced thereby.
The term glassy amorphous material, within the context of this description, defines those materials which typically exhibit only short-term ordering. The term is intended to include not only glasses, but also those "amorphous" materials which have any appreciable short-range ordering. However, it is intended to exclude both crystalline substances (such as silicon and silicon dioxide) and true amorphous materials having no appreciable ordering.
Glasses which comprise a specific class of glassy amorphous materials are typically quenched liquids having a viscosity in excess of about 10.sup.8 poise at ambient temperature. They are generally characterized by: (1) the existence of a single phase; (2) gradual softening and subsequent melting with increasing temperature, rather than sharp melting characteristics; (3) conchoidal fracture; and (4) the absence of crystalline X-ray diffraction peaks.
While the desirability of using glassy amorphous material in semiconductor devices has been long recognized, the development of semiconductor devices employing such materials has met only with limited success despite an intensive research effort. It is well known, for example, that glasses are easier to work with and less expensive compared with conventional crystalline semiconductors. However, many glassy amorphous materials are insulating materials. Thus, for example, typical oxidic glasses (glasses formed predominantly of oxide components) have not been considered useful in semiconductor devices because of their high resistivities and large band gaps.
Principally, three compositional groups of glasses have heretofore been found to possess sufficient conductivity to be classed as "semiconducting": the chalcogenide-halogenide glasses, the phosphate-borate-vanadate glasses, and the electro-optical glasses. Of these special composition glasses, only the chalcogenide glasses have been employed in workable semiconducting devices.
Moreover, glassy materials have historically been difficult materials in which to maintain compositional gradients of impurities. As a consequence, glassy devices utilizing sharply defined compositional gradients--such as those used in semiconductor junction devices--were not generally considered feasible because it was expected that any impurities would diffuse into the surrounding regions in a relatively short time.
For this reason, prior art devices using the above-mentioned semiconducting glasses have generally utilized only the bulk properties of the glass rather than junctions or junction-like effects.